package edu.cuit.avatar.concurrent;

import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

/**
 * @author <a href="mailto:1020zhaodan@163.com">Adan</a>
 * @version 1.0
 * @date 2025/7/17 13:41
 */
public class SemaphoreDemo {
    public static void main(String[] args) {
        var service = Executors.newCachedThreadPool();
        final Semaphore sp = new Semaphore(3);

        for (int i = 0; i < 10; i++) {
            Runnable runnable = new Runnable() {
                public void run() {
                    try {
                        sp.acquire();
                    } catch (InterruptedException e1) {
                        e1.printStackTrace();
                    }
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "进入，当前已有" + (3 - sp.availablePermits()) + "个并发");
                    try {
                        Thread.sleep((long) (Math.random() * 10000));
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "即将离开");
                    sp.release();
                    //下面代码有时候执行不准确，因为其没有和上面的代码合成原子单元
                    System.out.println("线程" + Thread.currentThread().getName() +
                            "已离开，当前已有" + (3 - sp.availablePermits()) + "个并发");
                }
            };
            service.execute(runnable);
        }
    }
}
